Ophthalmoscopy method

Abstract

A method is provided for observing structure and function of individual cells in a living human eye, comprising: using an adaptive optics optical coherence tomography (AO-OCT) system to image a volume of a retinal patch including numerous cells of different types, as for example, ganglion cells; using 3D subcellular image registration to correct for eye motion, including digitally dissecting the imaged volume; and using organelle motility inside the cell to increase cell contrast and to measure cell temporal dynamics.

We claim: 
     
       1. An ophthalmoscopy method, comprising:
 providing an adaptive optics optical coherence tomography (AO-OCT) system; 
 imaging retinal locations of a living subject using the AO-OCT system; 
 for each retinal location, acquiring AO-OCT video using the AO-OCT system focused at a retinal depth at which cells are to be imaged; 
 registering volumes in three dimensions; 
 averaging registered volumes across time points spaced such that natural motion of soma organelles enhances contrast between somas in retinal cells; 
 using spatial coordinates of the somas to determine soma stack depth, density and diameter; and 
 determining cell density measurements. 
 
     
     
       2. The method of  claim 1 , wherein the cells to be imaged are ganglion cells in the retinal ganglion cell (RGC) layer. 
     
     
       3. The method of  claim 1 , wherein the retinal locations included locations across a posterior pole of a human eye. 
     
     
       4. The method of  claim 1 , wherein using spatial coordinates of the somas includes determining at least one of soma size, density, reflectance and cell type. 
     
     
       5. An ophthalmoscopy method, comprising:
 segmenting contributions of RPE cells from rod outer segment tips; 
 averaging a registered RPE signal across time points spaced such that natural motion of cell organelles enhances cell contrast; and 
 characterizing a three-dimensional reflectance profile of individual RPE cells. 
 
     
     
       6. The method of  claim 5 , wherein characterizing a three-dimensional reflectance profile of individual RPE cells comprises characterizing a contribution of rod outer segment tips, RPE cell packing geometry, and a spatial relation to overlying cone photoreceptors. 
     
     
       7. An ophthalmoscopy system, comprising:
 an optical coherence tomography camera equipped with adaptive optics; 
 a controller comprising 
 registration software to correct eye motion to sub-cellular accuracy for stabilizing and tracking of cells in 4D, 
 a parallel computing module for real-time reconstruction and display of retinal volumes, and 
 at least one algorithm for visualizing and quantifying cells and cellular structures, including extracting biomarkers that reflect cell morphology and physiology. 
 
     
     
       8. A method for observing ganglion cells in a living human eye, comprising:
 using an adaptive optics optical coherence tomography (AO-OCT) system to image a volume of a retinal patch including a ganglion cell layer (GCL); 
 using 3D subcellular image registration to correct for eye motion, including digitally dissecting the imaged volume; and 
 using organelle motility inside GCL somas to increase cell contrast. 
 
     
     
       9. The method of  claim 8 , wherein a 3D resolution of the AO-OCT system is at least 2.4×2.4×4.7 μm 3  in retinal tissue. 
     
     
       10. The method of  claim 8 , wherein using organelle motility includes averaging images of the digitally dissected imaged volume to reduce speckle noise of the images. 
     
     
       11. The method of  claim 10 , wherein averaging images includes averaging images from more than 100 volumes of the retinal patch to increase clarity of the GCL somas. 
     
     
       12. The method of  claim 8 , wherein the GCL somas are one of stacked on each other, laying beneath a nerve fiber layer (NFL), or aggregated at a foveal rim of a macula. 
     
     
       13. The method of  claim 8 , wherein the volume covers a 1.5°×1.5° field of view of a retina. 
     
     
       14. The method of  claim 8 , wherein using 3D subcellular image registration includes obtaining videos of the volume over a time period and generating cross-sectional scans of the volume by sampling the video. 
     
     
       15. A system for observing ganglion cells in a living human eye, comprising:
 an adaptive optics optical coherence tomography (AO-OCT) system configured to image a volume of a retinal patch including a ganglion cell layer (GCL); and 
 an image post-processor configured to provide 3D subcellular image registration to correct for eye motion, including by digitally dissecting the imaged volume; 
 the image post-processor being further configured to use organelle motility inside GCL somas to increase cell contrast. 
 
     
     
       16. The system of  claim 15 , wherein a 3D resolution of the AO-OCT system is at least 2.4×2.4×4.7 μm 3  in retinal tissue. 
     
     
       17. The system of  claim 15 , wherein the image post-processor is configured to average images of the digitally dissected imaged volume to reduce speckle noise of the images. 
     
     
       18. The system of  claim 17 , wherein the image post-processor averages images from more than 100 volumes of the retinal patch to increase clarity of the GCL somas. 
     
     
       19. The system of  claim 15 , wherein the GCL somas are one of stacked on each other, laying beneath a nerve fiber layer (NFL), or aggregated at a foveal rim of a macula. 
     
     
       20. The system of  claim 15 , wherein the volume covers a 1.5°×1.5° field of view of a retina. 
     
     
       21. The system of  claim 15 , wherein the 3D subcellular image registration includes obtaining videos of the volume over a time period and generating cross-sectional scans of the volume by sampling the video. 
     
     
       22. A method of classifying cone photoreceptors in the living human eye from photostimulation-induced phase dynamics, comprising:
 measuring optical path length changes occurring inside cone photoreceptors during photoactivation to identify cone spectral types; 
 wherein measuring optical path length changes includes measuring optical path length changes in terms of an equivalent phase change by combining adaptive optics (AO) and phase sensitive optical coherence tomography (OCT) to reveal individual cone reflections in 3D. 
 
     
     
       23. The method of  claim 22 , further comprising using a single superluminescent diode with a central wavelength of about 790 nm and a bandwidth of about 42 nm for AO-OCT imaging. 
     
     
       24. The method of  claim 22 , further comprising using three fiber-based LED sources with spectra of 450±8 nm, 528±12 nm, and 637±12 nm, respectively, for stimulating cone photoreceptors. 
     
     
       25. The method of  claim 24 , further comprising estimating a proportion of photopigment bleached by the stimulation of the cone photoreceptors according to the equation: 
       
         
           
             
               
                 - 
                 
                   dp 
                   dt 
                 
               
               = 
               
                 
                   Ip 
                   
                     Q 
                     e 
                   
                 
                 - 
                 
                   
                     1 
                     - 
                     p 
                   
                   
                     t 
                     0 
                   
                 
               
             
           
         
         wherein p is the proportion of unbleached photopigment, I is the retinal illuminance, Q e  is a constant that denotes the flash energy required to bleach p from 1 to e −1 , and t 0  is the time constant of pigment regeneration. 
       
     
     
       26. The method of  claim 22 , further comprising classifying cone spectral type using slow dynamics of the cone photoreceptors by computing an average response for each cone. 
     
     
       27. The method of  claim 22 , further comprising classifying cone spectral type using fast dynamics of the cone photoreceptors by computing an average response over individual B-scans from a volume containing light stimulation for each cone. 
     
     
       28. A method for measuring temporal dynamics of cells, comprising:
 using an adaptive optics optical coherence tomography (AO-OCT) system operated at a center wavelength of about 790 nm to acquire volume videos at a location temporal to a fovea; 
 registering the volume videos to a reference volume to reduce motion artifacts; 
 characterizing fast temporal dynamics using an auto-correlation analysis to determine time constants for at least one of a nerve fiber layer, a ganglion cell layer and an inner plexiform layer; and 
 characterizing slow temporal dynamics using temporal speckle contrast on pixels of the volume videos, wherein the temporal speckle contrast includes determining a standard deviation of a reflectance amplitude and dividing the standard deviation by a mean of the reflectance amplitude.